The _generalissimo_ or commander-in-chief of an army is the person designated by the law of the land to take charge of the organized military forces of the state. In this country the President, through his Secretary of War, exercises this general command. In England, Wellington acts in the capacity of commander-in-chief of all the British military forces. In France, the Minister of War, under the king, has this general direction. In other European services, some prince of the blood, or distinguished general, exercises the functions of generalissimo. An active army in the field should be commanded by a _general_, or, as is done in some European countries, by a marshal. These may be regarded as of assimilated rank. A _corps d'armee_ should, be commanded by a _Lieutenant-general_. This rule is almost universal in Europe. The number of marshals in France under Napoleon was so great, that officers of this grade were often assigned to _corps d'armee_. A grand division of an army should be commanded by a _General of Division_. In England, the assimilated grade is that of major-general, and in France at the present time, the younger lieutenant-generals, or the _marechaux-de-camp_, command divisions. A brigade should be commanded by a _Brigadier-general_. At the present time in the French service, _marechaux-de-camp_ act as commanders of brigades. The several _corps d'armee_ are designated by numbers, 1st, 2d, 3d, &c., and in the same way the several divisions in each _corps d'armee_, and the several brigades in each division. When the number of troops are placed on a war footing, each _corps d'armee_ ordinarily contains from twenty to thirty thousand men. The command of these several _corps d'armee_, divisions, and brigades, is taken by the officers of the corresponding grades according to seniority of rank, and without reference to arms, unless otherwise directed by the generalissimo, who should always have the power to designate officers for special commands. The _chief of staff_ of an army is usually selected from the grade next below that of the general commanding, and receives the title, for the time being, which is used to designate this special rank. In some European armies, and formerly in our own service, this officer was called major-general. In France, if the generalissimo commands in person, a marshal is made chief of staff with the temporary title of _major-general_; but if a marshal commands the army, a lieutenant -general or _marechal-de-camp_ becomes chief of staff with the title of _aide-major-general_. The chiefs of staff of _corps d'armee_ and of divisions, are selected in precisely the same way. The position assigned by the commanding general for the residence of his staff, is denominated the _General Head-Quarter of the army_; that of a _corps d'armee_ staff, the _Head-Quarters of_ [1st or 2d, &c.] _corps d'armee_; that of a division, the _Head-Quarters of_ [1st or 2d, &c.] _division_, [1st or 2d, &c.] _corps d'armee_.